This study was initially conducted to evaluate the relationship between protease enzymology and platelet activation during the tissue factor induced clotting of minimally altered whole blood. These techniques are now being utilized in two different but related studies. In one study, patients with bleeding or clotting abnormalities, including various protein deficiencies, are studied. In the other study, various platelet inhibitors are added to the blood of normal individuals, and the coagulation process is then examined in the presence and absence of such inhibitors. In addition asprin will be administered to normal volunteers to examine the influence of aspirin in the blood clotting pathway. Subjects are tested for fibrinogen, prothrombin time and activated partial thromboplastin time and hemagrams and chem 13 profiles are obtained. Subjects in the study of the effects of aspirin are tested before aspirin is given and after receiving 650 mg/day aspirin for 3 days. In the study of platelet inhibitors, the inhibitor is present in one series of tubes to which blood is added and is absent in a control series.